Coating compositions



'- carbonate, 'asbestine and the like.

Pa'tentedMaraS,

FPlClE.

COATING COMPOSITIONS Andi- N. Laus, Newton, Mass, assig'nor to MonsantoChemical Company, St. Louis, Mo" a corporation of Delaware No Drawlng.-Application March 7,1942, Serial No. 433,733

; 18 Claims. (Cl.' 106.287)

This invention-relates to liquid coating compositions, and moreparticularly to coating compositions, such as varnishes, lacquers,synthetic resin coatings, and the like which contain sub- .stancescapable of reducing the gloss of the films formed therefrom. Glossreducing or flatting agents which have been used in the past includesuch substances as diatomaceous earth, clay, magnesia, magnesium Thesematerials, however, do not have a very highflatting efllciency, and areincapable of producing films which are sufliciently dull or flat tosatisfy exact ing requirements, such as those of the army' or navy. vMoreover, they are definitely unsuited for use in nitrocelluloselacquer'or like coating compositions, as they not only have a markedtendency to cake and settle in the lacquer vehicle, but cause hazinessor milkiness in clear films and a change of color (shade) or color value(intensity) in pigmented films, They also have a deleterious effect onthe general film properties of the lacquer, as shown by loss of tensilestrength, increase not tend to cake or settle in a lacquer vehicle.

A further object of the invention is to provide a flatting agent whichmay be added fto"clear lacquer compositions in suflicient quantity toproduce pronounced flatting efiects with substantially no change inthetransparency of the composition.

in brittling and early failure in the mandrel test.

A further object of the invention is to provide a flatting agent whichmay be added to pigmented lacquer compositions in suflicient amount toproduce pronounced 'flatting effects with substan tially no impairmentof the color or color value.

of the composition; a

A still further object of the invention is to provide a highly 'flattedlacquer composition which substantially retains the general filmproperties which it possessed prior to being flatted- A still furtherobject of the invention is to provide a fiatting agent of unusualflatting emciency which does not appreciably increase the viscosityand/or thixotropy or the coating compositions to which it is added uponbeing ground into or with said compositions.

A still further object of the invention is to provide a fiatting agentcomprising an organogel from which maximum amounts of the comm,

ous phase can be removed without diminishing the original fiattingpowers of thegel.

Stillfurther objects and advantages of the invention will'appear .fromthe following description and appended claims. Before explaining indetail the present invention, however, it is to be understood that theinvention is not. limited in its application to the details. describedherein, since the invention is capablejof other embodiments and of beingpracticed or: carried out in various ways. Also it is to be understoodthat the phraseology or terminology'employed herein is for the purposeof description and'not of limitation, and it is not intended to limitthe'invention claimed herein beyondthe requirements of the prior art. 1I

The present invention is ingeneral carried out by mixing with thecoating composition to be flatter varying amounts of a g'elof aninorganic oxide having an organic solvent as the liquid or continuous'phase, or at least as the major portion of the continuousphase. Thegels which it is proposed to use in the above manner are preferablypreparedby first preparing by any suitable method an aquagelcontaining an inorganic'oxide place the latter solvent by washing thegel with the water-immiscible organic solvent. Aportion at least of theorganic solvent is then removed by an ordinary evaporating or dryingoperation.

50 the like. However, it is possible to prepare com Organogels preparedin the above manner, but

with the drying step omitted, usually contain from 10' to 15% by weightof inorganic oxide, such as the oxide of silicon, aluminum, magnesium,titanium, tin, thorium, chromium, iron,nickel and mercially by the abovemethod gels containing prior to drying from 1 to about 20% by weight ofthe oxide. These undried org'anogels have excellent fiatting powers, butare in some instances undesirable for use as such, since they markedlyincrease the viscosity of the coating materials to which they are added,which not only renders the grinding of the treated materials diificult,but makes it hard to apply them by spraying methods.

The partially dried gels of the present invention may be prepared fromthe above undried gels in any desired manner. Usually a simple dryingoperation is resorted to, such as tumbling in a current of dry air.However, other methods such as evaporation by heat may also be employedwith equally good results. After being subjected to the drying treatmentthe gels contain anywhere from about 25 to 90% by weight of the oxideconstituting the solid or disperse phase of the gel.

Preferably, however, sufilcient of the organic solvent is removed toprovide a gel containing at characteristics, which are at the same timecapabio of producing highly fiat films, are not always obtained, whenless of the solvent is removed.

The partially dried, gels obtained as above are preferably added to thecoating compositions in amounts sufilcient to supply from 1 to 40% ofoxide based on the total solids in the final com- 7 least 40% of oxideby weight, as coating solutions or mixtures of thoroughly satisfactoryviscosity.

position. If larger amounts than this are employed the resulting film isapt tobe crackled or checked in appearance. The exact amount of oxidewhich is required in the coating composition depends upon the use whichis to be made of the particular coating composition being treated.Regardless of the amount employed or the use made of the coatingcomposition, however, the fiatting efliclency of the partially driedorganogels described herein is definitely superior to that of mostpreviously known fiat-ting agents.

It is essential that the amount of water in the continuous phase of theorganogel prior todry ing the same be as lowas possible, as the presenceof waterin the geltends to cause shrinkage during the drying andconsequent loss of fiatting power. However,in some instances it isunnecessary'to use a gel containing more than 40 to of oxide, assufiicient viscosity reduction is obtained with gels of thatconcentration, and in such cases it is possible to employ gelscontaining as much as 10 to 20% of water in the continuous phase withoutdiminishing the efiiciency of the gel as a fiatting agent to anyappreciable extent' In order to obtain a dried film of adequatesmoothness it is usually necessary to grind the gel into the'coatingcomposition. This may be accomplished in various ways, but is preferablydone by first preparing a so-called base grind, and then stirring thebase grind into sufiicient amounts of the vehicle of the coatingsolution to make a finished product ready for immediate .use or forstorage. Although grinding undried organogels into the coatingcomposition usually results in an undesirably thickened product, thepartially dried gels of this invention may be ground into the coatingcomposition without unduly increasing the viscosity of the final mixtureor solution with the result that the grinding operation itself isfacilitated, higher concentrations of gels may be ground into thecoating material and the product maybe handled more readily,

as for example in spraying operations.

A more thorough understanding of the illl tnasaaosi tion will beobtained from the following examples:

I Example I An aquagel is first made in the following manner: Fifty-twograms of oil of vitriol of 66 B. concentration (93.2% H2304) are addedto 500 grams of water, while maintaining the temperature at about 18 C.A solution of sodium silicate containing 29% S102 is then diluted with353 grams of water, and the resulting dilute solution is mixed with theabove sulfuric acid solution with agitation and cooling. The solution isthen allowed to gel, and the resulting gel is aged until full synaeresishas taken place. After ageing, the synaeresis liquor is removed and thegel is crushed to a V4 inch average lump size. The crushed gel is thenwashed with water until substantially all of the sodium sulfate isremoved.

The crushed and washed aquagel prepared in the above manner is coveredwith 95% ethyl alcohol. This alcohol and water mixture is then drainedoi! after about seven hours and replaced with fresh 95% alcohol. This isrepeated at intervals of 6 to 8 hours until the drained solvent has adensity between 0.819 and 0.822 at 20 C. (about CzHsOH). The resultingalcogel consists of approximately 13% silica, 78% ethyl alcohol and 9%water.

Two hundred grams of the alcogel obtained as described above arecrushed, and placed in a rothree-tenths grams of the above dried alcogelare I then placed in a porcelain pebble mill. To this is added about 200cubic centimeters of a lacquer having the following composition:

Percent by .weight Butyl acetate 29.0 Butyl almhnl 26.4 Toluene 32.7Castor ofl 5.6. a" nitrocellulose '6.3

The resulting mixture is ground for about threehours at 72 R. P. M.,which results in a smooth stable mass having a viscosity of 30centipoises which is suitable for use as a base grind.

An. exceedingly fiat finished lacquer is made from the above base grind.by diluting or letting down the grind with additional quantities of alacquer having the above formulation until the mixture or solution hasan SiOa content of about 15% by weight based on the film solids in theentire lacquer solution. The film obtained from this lacquer gives areading of 8 units when tested on the Hunter gloasmeter. A similar filmcontaining 15% silica xerogel gives a reading of only 28 units.

- Example II 'A crushedand washed aquagel prepared as described inExample I is covered with commercial acetone, and allowed to stand forabout seven hours. The liquid is then drained oi! the gel, and the gelis again flooded with fresh acetone. This procedure is repeated atintervals of 6 to 8 hours until the acetone drained oi! has aconcentration of 97% by weight. The resulting acetone gel is composed ofabout'14.2% silica, 83.8% acetone and 2% water. L

Two hundred grams of the acetone gel obtaine as described above arecrushed, and placed in a rotary drier. The gel is then dried in themanner described in Example I for a period of eight hours, which raisesthe silica concentration to 85.4%, by weight. Six and seven-tenths gramsof the above dried acetone gel are ground for about two and a halfhoursin a porcelain pebble mill with 300 cubic centimeters of a lacquerhaving the following composition:

Per cent by weigh Ethyl acetate 15.0 Butyl acetate 15.0 I Butyl alcohol20.0 Toluene 23.6 Rezyl 19 13.0 Dibutyl phthalate 4.1 6" nitrocellulose9.3

Upon completion of the grinding a finished on the solids in the lacqueris obtained. The lacquer thus treated does not settle on standing andforms a very smooth film which gives a reading of units when tested onthe Hunter glossmeter.

Example III Three hundred and eighty grams of aluminum nitrateA1(NOa)3'9H2O are first dissolved in 1200 cubiccentimeters of methylalcohol, cooled to about 10 C. and stirred vigorously while adding 280grams of redistilled aniline. The resulting mixture is allowed to reachroom temperature, at which time a firm jelly will have formed,

which can be extracted with methyl alcohol until- 1 .free of aniline andsalts. The alcohol-aluminum hydroxide jelly .or alcogel is crushed andwashed with commercial diethyl ether until substantially all ofthemethyl alcohol-has been replaced with the ether. The ether gel thusobtained is then dried in the manner described in Example I until thealumina concentration oithe gel is about 70% by weight.

Twenty-two and one-half grams of the dried alumina ether gel are groundfor about three hours in a porcelain pebble mill with 300 cubiccentimeters of a lacquer having the following composition:

' Per cent by weight Butyl alcohol 16.0 Toluene 67.5 Castor oil I 2.0Dibutyl phthalate X-low ethyl cellulose 13.0

A fiat finished lacquer is made from the above base grind by diluting orletting down the grind with additional quantities of a lacquer havingthe above formulation until the mixture or solution has an A120: contentof about 3% by weight based on the film solids in the entirelacquer-solution. The film obtained from this lacquer is exceedinglysmooth and is moderately flat.

Example IV Eighty=two grams of stannic chloride SnCl4-5Hz0 are dissolvedin 200 grams of water, and placed in a dializer, such as a sack made ofregenerated cellulose, as for example Cellophane, and is then suspendedin 2500 cubic centimeters of distilled water. After about 24 hours thecontents of the sack will have set to a firm jelly. This jelly is thenwashed with ethyl alcohol, until most of the water has been removed,after which the ethyl alcohol is replaced with ethyl acetate by repeatedwashing. .The thus prepared stannic oxide-ethyl lacquer having aboutsilica by weight based acetate organogel is crushed and dried in themafiner described in Example" 1 until the stannic =oxide concentrationof the gel is about 60% by weight.

Twenty-six and three tenths grams of the dried stannic oxide gel areground for about two hours in a porcelain pebble mill with 300 cubiccentimeters of a lacquer having the following composition:

Per cent by weight Ethyl acetate 30.0 Acetone 30.0 Methyl Cellosolve15.0 Santicizer 8 5.0 M-l'l a 5.0 Cellulose acetate E-27 15.0

An exceedingly flat finished lacquer is made from the above base grindby diluting or letting down the grind with additional quantities of-theabove lacquer until the mixture or solution has an SnOz content of about25% by weight based on the film solids in the entire lacquer solution.is obtained from this lacquer.

Example V Forty-four grams of magnesium nitrate Mg(NOa)2-6H20 aredissolved in a small amount of glycerine. and diluted to 50 cubiccentimeters. Thereafter, a second solution consisting of cubiccentimeters of diethyl amine and 65 cubic centimeters of glycerine isfloated on top of the above prepared magnesium nitrate solution. The twolayers are intimately mixed by shaking, and th resulting solutionallowed to set to a firm jelly. The continuous phase of the jelly, i. e.glycerine and water, is then replaced by continuouswashing ,with 1500grams of a phenolic resin varnish made 25 gallons long with China-woodoil and reduced from its original 50% solids to about 20% solids withSolvesso #3. ,The resulting varnish has an MgOcontent of 20% by weightbased on the film vsolids of the varnish, and forms an exceedinglysmooth fiat film.

Example VI Eighty-three grams of chromic nitrate Cr (N03) 3.9H2O

are dissolved in 100 cubic centimeters of water, to which there is thenadded with vigorous stirring 35 grams of ammonium acetate dissolved in50 cubic centimeters of water. Theuniform mixture sets in about 5minutes to a firm jelly. This v is crushed and washed with ethyl alcoholuntil substantially all of the water is removed. The. ethyl alcohol inthe gel is then replaced by continuous washing with Solvesso No. 1,which is a mixture of petroleum spirits and aromatic spirits having aboiling range between 94 and 139 C. The resulting chromic oxide gelhaving Solvesso No. 1 as its continuous phase is then dried in themanner described in Example I until the chromic v oxidefcontent ofthe'gel is about by weight.

Three hundred andseventy-five grams of the dried chromic oxide gel areground for about six hours in a gallon size porcelain pebble -mill with1000 grams of a pigmented synthetic air drying finish of the followingcomposition:

Per cent by weight Rezyl 807-1----4 52 Yellow iron oxide 17.4 Mediumchrome yellow 6.7 Lampblack 2.4 Solvesso No 3 21.1 Driers 0.4

The resulting synthetic resin solution has a CrzOa organogel content of36% by weight based on the.

film solids of the resulting solution and forms a smooth exceedinglyflat pigmented film.

A more thorough understanding of the effect of partially drying theorganogels on the viscosity of the base grind and on the fiattingetllciency of the organogel can be obtained from the following Butylacetate 29 Butyl alc 26.4 Toluene 37.7 Castor oil 5.6 nitrocellulose-6.3

The viscosities of'the resulting base grinds were then measured, afterwhich the various base grinds were let down with the same vehicle usedin the preparation of the base grinds to obtain lacquers having an S102content of 3% and respectively. The resulting lacquers were then driedto the form of a film and tested on the Hunter glossmeter:

Vi Lac uer fllm flatness Y Percent s in g ossmeter units l\c. of Sio init}? oi Type of gel dried lac ng drid guard in tie a ove el 3 S10 157510,. vehicle g: mm inamm 7oz Biol/g Anh drous" al- Poi-m coge l 0 1444.5 40 5 14% $102; 2% 2 25 6.3 43 7 H; 84% C12 4. 42. 5 1. 05 51 9HgOH. 8 85. 4 0. 98 49 10 7oz Slog/gal Commercial al-coge: 0 13 41.7 325 i "33 3'? it 3 13'7 SiOz; 9'7 4.

H020; 78% 0,; s 47.3 0. a 52 8 H5011. 8 63 0. 2 68 22 10 77 0.2 67 21 12oz Slo /gal Y 0 24. 3 so. 0 34 2 Silica ethcrgel 1 34 7.2 37 3 2 65 2.6' 45 5 12oz Si0,/gal

Commercial xerogel 100 1. 06 6b 28 Coating compositions obtained asdescribed above and in the examples and'containing the fiatting agentsof this invention form films which are exceedingly dull in appearance,i. e. low in specular reflection, and are admirably adapted for use onthe external surfaces of aeroplanes. battleships, and the like tofacilitate camouflage, and for similar uses. Clear coatings treated inaccordance with this invention are free of haziness-or milkiness, whilepigmented coatings containing the above described flatting agents retaintheir original color and color value. Moreover, the films formedtherefrom possess substantially the same tensile strength and resistanceto brittling as untreated coatings of otherwise the same composition.

The fiatting agents of this invention are also distinguished by the factthat they do not tend to increase the viscosity or the thixotropy of thecoating compositions to which they are added upon being ground intothem. Moreover. it is possible to employ a minimum amount of solvent inthe preparation of the gels, which not only tends to conserve solvent,but renders it unnecessary to shi large amounts of solvent to thelacquer or varnish manufacturer who uses the gels.

Although the preferred method of making the organogels of the presentinvention involves first forming an aquagel, and then replacing thewater therein with a suitable organic solvent, it is possible, asindicated in some of the. examples, to

form an organogel directly without going through the aquagel stage.

Reference has been made herein solely to the use of individual solventsin the preparation of the organogels. It is to be understood, however,that mixtures of these solvents may be employed, if desired, withequally good results, both in the preparation of. the gels and in theflatting efllciency of the resulting gels.

It is also to be understood that when the coating compositions of thisinvention are prepared by first making a base grind and then lettingdown, the grinding medium of the base grind may have the samecomposition as the coating composition employed in letting down, or itmay have any desired composition which is compatible with theingredients of the let down solution and is otherwise adapted togetherwith the let down a solution to form a satisfactory finished coatingcomposition. The base grind may also be made with anydesired'concentration of oxide which provides satisfactory grindingconditions.

The flattening agents of this invention have beendescribed as applicableprimarily to liquid coating compositions of all types. They may also beemployed however, in the flatting of plastic compositions, such ascellulose acetate, cellulose nitrate, styrene, methacrylate and likeplastic compositions, as well as in the fiatting of artificial silkcompositions.

The fiatting agents of this invention may also be used as pigments, thatis, they simultaneously act as insoluble coloring agents.

The term "Rezyl 19 is used herein to denote a glyceryl phthalate resinmodified with the acid of a non-drying oil, such as cocoanut oil. The

term Rezyl 8074 is used to denote a glyceryl phthalate resin modifiedwith the acid of a drying oil, such as linseed oil. The term X-low ethylcelluloseflis used to denote ethyl cellulose having an ethoxyl contentof 46.8 to 48.5% and a low viscosity, i. e. of the order of 13 to 15centipoises, when measured in the form of a 5% solution in a mixture ofparts of toluene and 20 parts of.

alcohol. The term .Santicizer 8" is used to denote a plasticizerconsisting essentially of ortho and para toluene ethyl sulfonamides. Theterm M-l'l is used to denote the plasticizer otherwise known as methylphthalyl ethyl glycollate. The term cellulose acetate E 27 is used todenote cellulose acetate having a viscosity varying from 1 to 4 secondsas measured by the A. S. T. M.

falling ball procedure, and an acetyl content varying from 39.6 to40.4%. The term Solvesso No. 3 is used to denote a hydrocarbon solventderived by solvent extraction and distillation of a petroleum base andcharacterized by a boiling range of 179 to 214 C. and by a high contentof aromatic constituents.

What I claim is:

l. A fiat coating composition comprising a film forming liquid of a typecommonly employed in varnishes, lacquers, synthetic resin solutions andthe like, and a relatively minor proportion of a partially dried andsubstantially unshrunk organogel having organic solvent as the majorportion of its liquid phase and an inorganic oxide as the solid phase,said organogel containing from 25 to 90% by weight of said inorganicoxide.

2. A fiat liquid coating composition comprising a film forming liquid ofa type commonly employed in varnishes,;lacquers, synthetic resinsolutions and the like, and a relatively minor proportion of a partiallydried ar id substantially unshrunk silica organogel having organicsolvent as the major portion of its liquid phase, said organogelcontaining from 25 to 90% by weight of silica.

3. A fiat liquid coating composition comprising a film forming liquid ofa type commonly em-' ployed in varnishes, lacquers, synthetic resinsolutions and the like, and a relatively minor proportion of a partiallydried and substantially unof alumina.

ing a lacquer and a relatively minor proportion of a partially dried andsubstantially unshrunk silica alcogel, said alcogel containing from 25to 90% by weight of silica.

9. A fiat liquid coating composition comprising a varnish and arelatively minor proportion of a partially dried and substantiallyunshrunk silica toluene gel, said gel containing from 25 to 90% byweight of silica.

10. A fiat liquid coating composition comprising a pigmented syntheticresin solution and a relatively minor proportion of a partially driedand substantially unshrunk silica gel having petroleum sp'iritsas theliquid phase, said gel con- 4. A fiat liquid coating compositioncomprising 7 a film forming liquid of a type commonly employed invarnishes, lacquers, synthetic resin solutions and the like, and arelatively minor :proportion of apartially dried and substantiallyunshrunk iron oxide organogel having organic solvent as the majorportion of its liquid phase, said organogel containing from 25 to 90% byweight of iron oxide.

5. A fiat liquid coating composition comprising a lacquer and arelatively minor proportion of a partially dried and substantiallyunshrunk organogel having organic solvent as the major portion of itsliquid phase and an inorganic oxide as the solid phase, said organogelcontaining from 25 to 90% by weight of said inorganic' oxide.

6. A fiat liquid coating composition comprising a clear varnish and arelatively minor 'proportion of a partially dried and substantiallyshrunk organogel having organic solvent as the major portion of itsliquid phase and an inorganic oxide as the solid phase, said' organogelcontaintaining from 25 to 90% by weight of silica.

11. A fiat liquid coating composition comprising a film forming liquidof a type commonly employed in varnishes, lacquers, synthetic resinsolutions and the like, and a partially dried and substantially unshrunkorganogel having organic solvent as the major proportion of its liquidphase and an inorganic oxide as the solid phase, said organogelcontaining from 25 to 90% by wm'gh-t of said inorganic oxide and beingpresent in an amount sufiicient to provide from 1 to'40% by weight ofsaid inorganic'oxide based on the soli in said film forming liquid.

12. A fiat liquid coating composition comprising a film forming liquidof a type commonly employed in varnishes, lacquers,'synthetic resinsolutions and the like, and a partially dried and substantially unshrunksilica alcogel containing from 25 to 90% by weight of silica, and saidalcogel being present in anamount suflicient to pro-- vide from 1 to 30%by weight of silica based on the solids in said film forming liquid.

13. A liquid coating composition which dries to form a fiat film,comprising a film forming liquid of a type commonly employed invamishes, lacquers, synthetic resin solutions and the like, I to whichthere has been added a partially dried and substantially unshrunkorganogel having organic solvent as the major portion of its liquidphase and an inorganic oxide as the solid phase,

said organogel containing from 25- to 90% by a weight of said inorganicoxide and being present in an amount suflicient to provide from 1 to 10%by weight of said inorganic oxide based on the I solids in said filmforming liquid.

14. A liquid coating composition which dries to iorm a fiat film,comprising a film forming liquid tions and capable of imparting a fiatfinishto a film obtained therefrom comprising a ground mixture of apartially dried and substantially unshrunk organogel having organicsolvent as the major portion of its liquid phase said organ-- ogelcontaining from 25 to by weight of said inorganic oxide, and aninorganic oxide as the sition.

16. A flatting composition to be added in relatively small amounts toliquid coating compositions and capable of imparting a flat finish to afilm obtained therefrom comprising a ground mixture of a partially driedand substantially unshrunk silica alcogel, said alcogel containing from25 to-90% by weight of silica, and a liquid vehicle therefor which iscompatible with a solvent of said coating composition.

1'7. The method of flatting liquid coating compositions of the type ofvarnishes, lacquers, synthetic resin solutions and the like;whichcomprises first forming a base grind by grinding into a liquidvehicle compatible with said coating composition a partially dried andsubstantially unshrunk organogel having organic solvent as the majorportion oi'its liquid phase said organogel containing from 25 to 90% byweight of said inorganic oxide and an inorganic oxide as the solidphase, and then letting down the resulting base grind with suiflcient ofsaid coating composition .to provide a final coating solution having ,aninorganic oxide content between 1 and 40% by weight based on the solidsin said final coating solution.

18. A flatting agent comprising a partially dried and substantiallyunshrunk organogel containing from 25 to 90% by weight of an inorganicoxide and having organicsolvent as the major portion of its liquidphase, said flatting agent exerting a pigmenting action.

ANDRE N. mus.

